Phosphocholine conjugates have been studied extensively because phosphocholine (PC) is thought to play a vital role in the pathogenesis of pathogenic microorganisms, such as Streptococcus pneumoniae. Some reports suggest that by binding to the platelet activating factor receptor on epithelial and endothelial cells, PC facilitates transport of S. pneumoniae into the blood and brain. Furthermore, PC has been found to be an immunodominant epitope on the surface of many pathogenic microorganisms, including but not limited to S. pneumoniae, Streptococcus oralis, Streptococcus sanguis, Streptococcus spp., Clostridium spp., Lactococcus spp., Bacillus spp., Haemophilus influenzae, Haemophilus aphrophilus, Proteus morganii, Actinomyces naeslundii, Actinobacillus actinomycetemcomitans, Fusobacterium nucleatum, Neisseria meningitidis, Trichinelia spiralis, Acanthocheilonema viteae, Leishmania major, Trypanosoma cruzi, Schistosoma mansoni, Diphyllobothrium latum, Toxicara canis (second stage larvae), Acanthocheilonema viteae, and Litomosoides sigmodontis. 
S. pneumoniae is surrounded by a capsule composed of complex carbohydrates. This capsule is the primary virulence factor for S. pneumoniae, providing a mechanism for the bacteria to prevent destruction by macrophages and polymorphonucleocytes. S. pneumoniae also has a cell wall composed of proteins and carbohydrates. The carbohydrate portion of this cell wall has the hapten PC as the major antigenic determinant.
One class of PC conjugates is a hapten PC conjugated to a carrier. A commonly utilized hapten PC, p-diazophenylphosphocholine (DPPC), has been conjugated to protein antigens to produce high affinity phenylphosphocholine-(PPC) specific antibodies; however, unfortunately, these antibodies are not found to be protective against S. pneumoniae. 
In contrast, conjugates of the phosphocholine ester p-nitrophenyl-6-(O-phosphocholine)hydroxyhexanoate (“EPC”) have been shown to elicit a PC-specific antibody response. A method of synthesizing EPC is known as described in Spande, T F, “Synthesis of two novel phosphorylcholine esters for probes in immunogenic studies,” J. Org. Chem. 45:381-84, 1980. This method, however, is elaborate as it requires many reaction steps to form EPC from the initial reactants 2-bromoethylphosphorodichloridate and tert-butyl 6-hydroxyhexanoate.
Although EPC and a method of synthesizing EPC are known, there is still a need for new methods of synthesizing EPC and derivatives thereof, particularly methods that are more efficient and cost-effective. Additionally, there is a need to develop new phosphocholine conjugates that can effectively prevent microorganism infections, including conjugates of EPC and its derivatives. The present invention is directed to these, as well as other, important needs.